Implantable neurostimulation devices can be employed to manage pain arising from a variety of conditions such as failed back surgery syndrome, post-laminectomy syndrome or other neuropathies. To this end, a spinal cord stimulation (SCS) device or other neurostimulator may be implanted within the body to deliver electrical pulses to nerves or other tissues. The neurostimulator typically includes a small pulse generator device similar to a pacemaker but equipped to send electrical pulses to leads mounted along the nerves near the spinal cord or elsewhere. For SCS, the generator is often implanted in the abdomen or buttock area. The stimulation leads may include thin wires or paddles for delivering electrical pulses to patient nerve tissues. An external controller, similar to a remote control device, may be provided to allow the patient to control or adjust the neurostimulation. Currently, prior to permanent (i.e. chronic) implant of a neurostimulator, the patient undergoes a trial period during which he or she is implanted with a lead that is externalized and connected to a trial neurostimulation control device, which the patient carries with him or her. Herein, the external neurostimulation control device used during the trial period is referred to as a trial neurostimulator or trial neurostimulation device.
State-of-the-art implantable neurostimulators and trial neurostimulators are being designed to communicate with tablet computers, smartphones and other mobile instruments to allow the patient or clinician to control the operation of the device, retrieve diagnostic data, etc. For example, dedicated application software (i.e. an “app”) running on a tablet computer could be used to adjust the frequency or amplitude of neurostimulation applied to the spine by an SCS device to allow the patient to improve pain reduction. In particular, Bluetooth Low Energy (BLE) telemetry protocols can be used to control communication between a mobile instrument and an implantable neurostimulator or trial neurostimulator. Issues, however, arise in implementing such a communication scheme. App designers typically have minimal control over the behavior of the mobile device platform, which may comprise a commercially off-the-shelf mobile instrument employing build-in drivers and operating systems. The designers of apps for communicating with neurostimulation devices may have only a limited level of configuration control on the BLE protocol stack. Furthermore, conservation of the power supply of an implantable medical device is a key design issue. It is important to avoid undue depletion of battery resources. This is particularly true insofar as “wake-up and pairing” is concerned wherein the implantable neurostimulator and the mobile instrument detect one another's presence and establish secure communications. Similar concerns apply to external trial neurostimulators, which may be provided with only minimal power resources since the trial period is typically a month or less. Accordingly, there is the need to implement a wake-up and pairing scheme that provides a robust link with minimal impact on the longevity of neurostimulator devices or other implantable or trial medical devices.
However, the standard wake-up and pairing scheme for connecting a Bluetooth accessory device (i.e. a slave device) to a mobile instrument (such as a tablet computer) is for the accessory device to periodically “advertise” itself so that a mobile instrument in the vicinity might be alerted to its presence. The mobile instrument then tags to one of the advertising pulses and requests a connection, i.e. an initial “handshake” is performed. Pairing or normal link establishment then follows the initial handshake. However, most of the advertisement signals generated by the accessory device are unheeded because no mobile instrument is nearby to establish a connection. For implantable neurostimulators, the standard wake-up and pairing scheme could significantly deplete the battery resources of the implanted device. Similar battery depletion problems can arise during a trial neurostimulation period when wirelessly connecting an external trial neurostimulator to a mobile instrument. Still further, problems can arise involving malicious “spoofing” or “hacking” if the neurostimulator is programmed to transmit frequent advertisement signals that a rogue external instrument might intercept. Indeed, even if the neurostimulator properly rejects communication requests with a rogue device, considerable battery energy could be wasted while the neurostimulator filters out the invalid requests. Similar problems could also occur with other implantable medical devices such as pacemakers if equipped to communicate with external instruments using Bluetooth or other wireless communication protocols.
Accordingly, it would be highly desirable to provide improved techniques for performing wake-up and pairing (or similar protocols) between implantable/external medical devices and mobile instruments such as tablet computers. It is to these ends that aspects of the invention are generally directed.